Biofuels and biomass
This article is based on the lecture that Stanley Hirsch gave at the AACI on Sunday 23rd December. He works for a company called Futuragene, that has offices in London and Rehovot and that specializes in uses of biofuels and biomass for energy production.
So far we are dependent on so-called fossil fuels (oil and coal) derived from the degradation of ancient fossils deep underground for most of our energy needs. For transportation 95% of our needs is supplied by gasoline. But, this dependence has three drawbacks, first it has become very expensive (crude petroleum is now $95 per barrel, when it was $40 during the energy crisis of 1973), second it is polluting (producing excess carbon dioxide into the atmosphere, causing global warming) and third it is running out (not rapidly, but easy sources are diminishing). Because of these reasons it is necessary to find alternative sources to fossil fuels for energy production.
The main alternative fuel to gasoline currently being developed to run our cars is ethanol. It should be noted that so-called "hybrid" cars, that use partial dependence on electrical motors that are charged by the gasoline engines, are more efficient than gasoline alone, but do not solve the problem of additional carbon dioxide being added to the atmosphere. The main advantage of ethanol as a "biofuel" is that it can be produced from plants grown from the earth by farming rather than from fossil fuels, the carbon of which has been trapped underground for eons. In this way the biofuels allow a cycle of returning carbon to the air that has been taken up by the plants during their growth, thus not adding additional carbon dioxide and not causing global warming.
Plants that produce ethanol on breakdown are cereal crops (mainly corn), and sugar crops (mainly sugar cane, beets and sweet sorghum). The process is simplest from sugar cane, which can be crushed to yield a sugar solution of ca. 75% glucose that can be fermented directly in large-scale industrial fermentors to produce ethanol (similar to the production of wine or beer). This process is being used extensively in Brazil, that has turned a large proportion of its land over to sugar cane production and now runs many of its buses and cars on ethanol:gasoline mixtures (from 10% E10 up to 85% E85). The main problem of ethanol is that it cannot be pumped in pipelines (due ot its vapro pressure) and tends to corrode normal engines at greater than 15% mixture, so engines have to be modified. One advantage of ethanol is that the percent of ethanol can be varied and many engines automatically adjust themselves to the mixture used.
In order to make the process economic it is necessary to use a large area of farmland to produce large quantitiies of the crop and have largescale fermentors producing ethanol on industrial scale. Since large areas of land are currently producing corn, and corn can be used to produce ethanol by extracting starch and then degrading it into sugar (glucose) and then fermenting it as before, corn is being used in the US and elsewhere as a source of ethanol. But, the energy yield of corn is only about 1.3 units for every unit of energy required to produce ethanol while sugar cane comparably produces 8 units of energy, so it is 6 times more efficient to use sugar cane than corn. However, the corn manufacturers in the US are a very influential lobby and so corn is being used for this purpose. Some of the corn for ethanol is being grown on land that was previously producing food, and this has caused the price of corn in the US to soar and has lead to food riots in Mexico, where the cost of the main food item, tortillas made from corn, has rocketed. However, the source of biofuels depends a lot on the climate and the available crops.
China now realizes that it has caused dangerous pollution, for example in Beijing where there is a problem for the Olympics, and so they are entering on a crash course to produce ethanol in place of gasoline. Also, note that this will help to make them energy self-sufficient if they grow their own biofuel crops rather than import gasoline.
The use of crops for biofuels is only one example of a larger scale transition from fossil fuels to the use of biomass, large industrial masses of agricultural production that can be used to produce either a fuel or can be burnt directly to produce steam to drive turbines to generate electricity. Note that some trees such as spruce (that is thin, straight and has few branches) can be grown in large plantations and harvested for biomass. However, to make the whole process much more efficient, it is preferable to modify the plants genetically to be more efficient for the process intended. It is now also possible to produce butanol in place of ethanol which can be pumped in pipelines and does not corrode normal engines.
There are many other alternative sources of energy and fuels, including wind turbines and many types of plants (such as palm trees being grown in Africa and Asia to produce oil), so the outlook is for many varied approaches that will be used in parallel depending on the particular circumstances and efficiencies. One thing can be said with certainty, in the future our dependence on oil will definitely be reduced.
So far we are dependent on so-called fossil fuels (oil and coal) derived from the degradation of ancient fossils deep underground for most of our energy needs. For transportation 95% of our needs is supplied by gasoline. But, this dependence has three drawbacks, first it has become very expensive (crude petroleum is now $95 per barrel, when it was $40 during the energy crisis of 1973), second it is polluting (producing excess carbon dioxide into the atmosphere, causing global warming) and third it is running out (not rapidly, but easy sources are diminishing). Because of these reasons it is necessary to find alternative sources to fossil fuels for energy production.
The main alternative fuel to gasoline currently being developed to run our cars is ethanol. It should be noted that so-called "hybrid" cars, that use partial dependence on electrical motors that are charged by the gasoline engines, are more efficient than gasoline alone, but do not solve the problem of additional carbon dioxide being added to the atmosphere. The main advantage of ethanol as a "biofuel" is that it can be produced from plants grown from the earth by farming rather than from fossil fuels, the carbon of which has been trapped underground for eons. In this way the biofuels allow a cycle of returning carbon to the air that has been taken up by the plants during their growth, thus not adding additional carbon dioxide and not causing global warming.
Plants that produce ethanol on breakdown are cereal crops (mainly corn), and sugar crops (mainly sugar cane, beets and sweet sorghum). The process is simplest from sugar cane, which can be crushed to yield a sugar solution of ca. 75% glucose that can be fermented directly in large-scale industrial fermentors to produce ethanol (similar to the production of wine or beer). This process is being used extensively in Brazil, that has turned a large proportion of its land over to sugar cane production and now runs many of its buses and cars on ethanol:gasoline mixtures (from 10% E10 up to 85% E85). The main problem of ethanol is that it cannot be pumped in pipelines (due ot its vapro pressure) and tends to corrode normal engines at greater than 15% mixture, so engines have to be modified. One advantage of ethanol is that the percent of ethanol can be varied and many engines automatically adjust themselves to the mixture used.
In order to make the process economic it is necessary to use a large area of farmland to produce large quantitiies of the crop and have largescale fermentors producing ethanol on industrial scale. Since large areas of land are currently producing corn, and corn can be used to produce ethanol by extracting starch and then degrading it into sugar (glucose) and then fermenting it as before, corn is being used in the US and elsewhere as a source of ethanol. But, the energy yield of corn is only about 1.3 units for every unit of energy required to produce ethanol while sugar cane comparably produces 8 units of energy, so it is 6 times more efficient to use sugar cane than corn. However, the corn manufacturers in the US are a very influential lobby and so corn is being used for this purpose. Some of the corn for ethanol is being grown on land that was previously producing food, and this has caused the price of corn in the US to soar and has lead to food riots in Mexico, where the cost of the main food item, tortillas made from corn, has rocketed. However, the source of biofuels depends a lot on the climate and the available crops.
China now realizes that it has caused dangerous pollution, for example in Beijing where there is a problem for the Olympics, and so they are entering on a crash course to produce ethanol in place of gasoline. Also, note that this will help to make them energy self-sufficient if they grow their own biofuel crops rather than import gasoline.
The use of crops for biofuels is only one example of a larger scale transition from fossil fuels to the use of biomass, large industrial masses of agricultural production that can be used to produce either a fuel or can be burnt directly to produce steam to drive turbines to generate electricity. Note that some trees such as spruce (that is thin, straight and has few branches) can be grown in large plantations and harvested for biomass. However, to make the whole process much more efficient, it is preferable to modify the plants genetically to be more efficient for the process intended. It is now also possible to produce butanol in place of ethanol which can be pumped in pipelines and does not corrode normal engines.
There are many other alternative sources of energy and fuels, including wind turbines and many types of plants (such as palm trees being grown in Africa and Asia to produce oil), so the outlook is for many varied approaches that will be used in parallel depending on the particular circumstances and efficiencies. One thing can be said with certainty, in the future our dependence on oil will definitely be reduced.
posted by Jack Cohen at 1:14 PM
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